Synthesis and photophysical properties of polyethylene containing pyrenyl units in the side chain

Copolymerization of ethylene and diallyl-bis(pyren-1-yl)-silane (APyS) was investigated with zirconocene catalysts, rac-ethylenebis(indenyl)zirconium dichloride (1) and diphenylmethylene(cyclopentadienyl)(9-fluorenyl)zirconium dichloride (2), using methylaluminoxane as a cocatalyst. APyS was copolymerized via both 1,2-insertion and cyclization insertion, and cyclization selectivity, ratio of cyclized insertion unit, of APyS in the copolymers obtained with Catalyst 1 was higher than that obtained with Catalyst 2. Catalyst 2 showed a higher reactivity for APyS than Catalyst 1. Photophysical properties of the copolymer were investigated by UV-vis and photoluminescence (PL) spectroscopy, and absorption and fluorescence derived from pyrenyl groups were detected in the copolymers. Chloroform solution of the copolymer showed emission derived from both monomer and eximer of pyrenyl units. Only the emission derived from eximer of pyrenyl units was observed in the cast film. The polarized PL spectrum of an oriented film showed anisotropy, and the polarization excitation parallel to the drawing direction showed high fluorescence intensity.